Chapter 5, Problem 5.40P

Three sub steps of a thermodynamic cycle are employed in order to change the state of a gas from 1 bar, 1.5 cubic meter and internal energy of 512 kJ. The processes are: 1st step: Compression at constant PV to a pressure of 2 bar and internal energy of 690 kJ. 2nd step: A process where work transferred is zero and heat transferred is - 150 kJ. 3rd step: A process where work transferred is -50 kJ. without KE and PE changes, determine: a. heat transferred during 1st step (kJ) b. heat transferred during 3rd step (kJ)

Between a heat source at temperature T and a low-temperature heat well at 280 K power cycle is working. In steady state, the cycle produces 50 kW of work, while the heat well is 1000 kl/min. heats up. Determine the minimum theoretical value for T in K (Kelvin).

Problem 1 - Refrigerator A refrigerator operates at steady state with a coefficient of performance of 4.5 and a power input of 0.8 kW. Energy is rejected from the refrigerator to the surroundings at 20°C by heat transfer from metal coils attached to the back. Determine (a) the rate energy is rejected, in kW. (b) the lowest theoretical temperature inside the refrigerator, in K.

C5 6.

The refrigerator shown in the figure below operates at steady state with a coefficient of performance (COP) of 5.0 within a kitchen at 23 °C. The refrigerator rejects 4.8 kW by heat transfer to its surroundings from metal coils located on its exterior. Determine: (a) the power input, in kW.(b) the lowest theoretical temperature inside the refrigerator, in K.

An air conditioner is a device used to cool the inside of a home. It is, in essence, a refrigerator in which mechanical work is done and heat removed from the (cooler) inside and rejected to the (warmer) outside. A home air conditioner operating on a reversible Carnot cycle between the inside, absolute temperature T2, and the outside, absolute tempera- ture T1 > T2, consumes P joules/sec from the power lines when operating continuously. (a) In one second, the air conditioner absorbs Q2 joules from the house and rejects Q1 joules outdoors. Develop a formula for the efficiency ratio Q2/P in terms of T1 and T2. (b) Heat leakage into the house follows Newton's law Q = A(T, – T2). Develop a formula for T, in terms of T1, P, and A for continuous operation of the air conditioner under constant outside temperature T and uniform (in space) inside temperature T2. (c) The air conditioner is controlled by the usual on-off thermostat and it is observed that when the thermostat set at 20°C and an…

2. A thermal machine operates in a carnot cycle between temperatures 820 ° C and 18 ° C. Calculate for each kw of net power that yields: a) The amount of heat that is supplied and discharged in kj/h and b) thermal efficiency.

As shown in the figure, an air conditioner operating at steady state maintains a dwelling at 70°F on a day when the outside temperature is 90°F. The rate of heat transfer into the dwelling through the walls and roof is 30,000 Btu/h and the net power input to the air conditioner compressor is 3 hp.    Determine   a. the coefficient of performance for the air conditioner b. power input required in hp c.  coefficient of performance for a reversible air conditioner providing the same cooling effect while operating between the same cold and hot temperatures.

A power cycle operates between hot and cold reservoirs at 900 K and 300 K, respectively. At steady state the cycle develops a power output of 0.38 MW while receiving energy by heat transfer from the hot reservoir at the rate of 1 MW.Determine the thermal efficiency and the rate at which energy is rejected by heat transfer to the cold reservoir, in MW for the following.(a) The power cycle and conditions above. Determine the thermal efficiency and the rate at which energy is rejected by heat transfer to the cold reservoir, in MW.(b) A reversible power cycle operating between the reservoirs and receiving the same rate of heat transfer from the hot reservoir as in part (a). Determine the thermal efficiency and the rate at which energy is rejected by heat transfer to the cold reservoir, in MW.